• Using data collected in the National Institute of Mental Health Epidemiologic Catchment Area Program, we examined the reported age at onset of selected mental disorders using life table survival methods. The examination of hazard rates suggests that adolescence and young adulthood are important periods for the development of unipolar major depression, bipolar illness, phobias, and drug and alcohol abuse/dependence. Although there are limitations in using cross-sectional data for this purpose, the findings suggest the need for more attention to the development of mental disorders in childhood and adolescence.